may be highjacking this thread but ... can anyone explain just why GM now requires dexos spec oil???recently bought a 2011 Impala with 3.5L LZE that owners manual says needs dexos1.of course the 3.5L has been in production for a number of years ... and I am sure a 2010 or earlier 3.5L is no different than my 2011 3.5L so why the new "mandate" from GM???

FWIW ... haven't yet changed out the dealer installed unknown oil but will do so soon as OLI is at ~ 43% ... QSGB is probably what will end up in the crank case

may be highjacking this thread but ... can anyone explain just why GM now requires dexos spec oil???recently bought a 2011 Impala with 3.5L LZE that owners manual says needs dexos1.of course the 3.5L has been in production for a number of years ... and I am sure a 2010 or earlier 3.5L is no different than my 2011 3.5L so why the new "mandate" from GM???

FWIW ... haven't yet changed out the dealer installed unknown oil but will do so soon as OLI is at ~ 43% ... QSGB is probably what will end up in the crank case

Probably to attempt for their consumers to use a better motor oil than Lubestation 3000XL brand from the place offering $16.99 changes. I'm sure people are still running the OLM down to 0% on sub par oil and filters.

may be highjacking this thread but ... can anyone explain just why GM now requires dexos spec oil???

All their DI and/or turbocharged engines needed a stouter oil to deal with the demands of the engine. Those new engines are pretty hard on oil, and need it changed by the time the OLM says to. If not before.

I've used Original GM 5w30 synthetic Dexos1 (made by Cosan that makes also Mobil 1 in here, so I figure if this is M1 actually) in my cars. My Subaru with 122k miles doesn't like any 5w30 anymore, or I don't like the way it sounds with any 5w30 when at op temps. In the Taurus, is fine, no weird sounds at all (good old Vulcan). I'm still on GM Leget in the Taurus, it just uses a little more oil than with M1 15w50 at road speeds, because of the lower viscosity (they are both M1 syn in my opinion, but Cosan didn't answered my question if they are the same oil for cost production reasons). City driving isn't giving greater consumption, just at highway long trips (470 miles straight).